Alva Campbell, Raymond Tibbetts and other death-row inmates sued Ohio in 2011, alleging that the state’s current three-drug execution protocol, which includes the controversial sedative midazolam, violates the Eighth and 14th Amendments of the U.S. Constitution.

Those opposed to the death penalty say Ohio’s dose of sedative does not do enough to render inmates unconscious and prevent pain as medical personnel administer the two other drugs in the combination.

Ohio was forced to suspend executions in 2015 after running out of lethal injection drugs. It resumed executions last July after midazolam became available. Florida, Oklahoma, Alabama, Virginia, and Arkansas have used the sedative as part of three-drug protocols. Inmates in other states have mounted legal challenges.

Campbell wants to delay his execution for the aggravated murder of 18-year-old Charles Dials during a 1997 carjacking.

Tibbetts was sentenced to death for the 1997 stabbing of Fred Hicks in Cincinnati. He was also sentenced to life in prison for stabbing and beating his 42-year-old wife Judith Crawford to death.

This past November, U.S. Magistrate Judge Michael Merz in Dayton, Ohio, ruled that the two men had not made clear that the injection protocol violates their constitutional rights by posing an unacceptable risk of pain and suffering. The judge denied their motion for a stay of execution.

On appeal to the Sixth Circuit, the inmates argued that the 500-milligram dose of midazolam was ineffective. Even if it worked, they said, execution staff do not wait long enough before administering the painful drug rocuronium bromide to paralyze inmates.

A three-judge panel led by U.S. Circuit Judge Alice Batchelder rejected those arguments Thursday.

Batchelder wrote in a nine-page opinion that Campbell and Tibbetts provided no scientific evidence to support the so-called “unseen effects” of the state’s dose of midazolam, and relied too heavily on visual cues from other executions – gasping, crying and other movements – that were difficult to quantify.

“We agree with this determination and find that, as with the prior claim, Tibbets [sic] and Campbell’s inability to produce scientific evidence about the unseen effects of a 500-mg dose of midazolam leave them unable to prove that the execution protocol as a whole is sure or very likely to cause serious pain,” Batchelder wrote.

Campbell’s attorney, David Stebbins, said Thursday he was reviewing the ruling and could not immediately comment.

Ohio Governor John Kasich’s office did not immediately respond to a request for comment.

Gary Daniels of the American Civil Liberties Union of Ohio said the state has an “international reputation for screwing up executions” and it had not even taken “modest steps” to improve its death penalty procedures.

“It looks like we’re going keep doing what we always do here in Ohio, keep using this particular drug,” Daniels said in a phone interview. “We can’t help but think it’s going to lead to more botched executions, and unfortunately this is done with the consent of our courts, our legislature and our governor, who’ve taken no meaningful actions with regard to the death penalty.”

Last year, Ohio executed its first death-row prisoner since 2014. The inmate, Ronald Phillips, had also challenged the constitutionality of Ohio’s lethal drugs combination. He was convicted of killing his girlfriend’s 3-year-old daughter, Sheila Marie Evans, in Akron.

Ohio’s lethal injection procedures have been beset with problems. An official took 25 minutes to declare inmate Dennis McGuire dead in January 2014. The state was testing a new two-drug combination on him. Witnesses reported that McGuire snorted, gasped and choked before he died.

That was the last execution before Phillips in July 2017. Convicted murderer Gary Otte was executed in September.

Campbell was granted a reprieve when officials called off his execution in November because they couldn’t find a usable vein to inject him with lethal drugs. His execution has been rescheduled for June 5, 2019.

Tibbetts’ execution is scheduled for Feb. 13, less than two weeks after the Sixth Circuit denied him relief.

Governor Kasich has faced calls in recent weeks to spare Tibbetts because attorneys say he suffered from opioid addiction. On Thursday, a former juror in Tibbetts’ capital murder trial wrote a letter urging Kasich to grant him a reprieve.

The juror said he has since seen mitigating evidence that he had never seen at trial and he would not have recommended the death penalty if he heard about Tibbetts’ history of abuse and addiction.

U.S. Circuit Judges John Rogers and Amul Thapar rounded out the Sixth Circuit panel.